diff --git a/CHANGELOG.md b/CHANGELOG.md
index f9547ff7..49200d0e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - An abstraction over hblank DMA to allow for cool effects like gradients and circular windows. See the dma_effect* examples.
 - Expermental and incomplete support for MIDI files with agb-tracker.
 - Fixnum now implements [`num::Num`](https://docs.rs/num/0.4/num/trait.Num.html) from the [`num`](https://crates.io/crates/num) crate.
+- `Default` implementations for `RandomNumberGenerator`, `InitOnce` and `RawMutex`.
 
 ### Change
 - A few functions which previously accepted a `Vector<u16>` now accept an `impl Into<Vector2D<u16>>` instead.
diff --git a/agb/src/rng.rs b/agb/src/rng.rs
index f0ef404f..b98ad6ce 100644
--- a/agb/src/rng.rs
+++ b/agb/src/rng.rs
@@ -52,6 +52,12 @@ impl RandomNumberGenerator {
     }
 }
 
+impl Default for RandomNumberGenerator {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 static GLOBAL_RNG: Mutex<RefCell<RandomNumberGenerator>> =
     Mutex::new(RefCell::new(RandomNumberGenerator::new()));
 
diff --git a/agb/src/sync/locks.rs b/agb/src/sync/locks.rs
index fdb7033f..2c2cd952 100644
--- a/agb/src/sync/locks.rs
+++ b/agb/src/sync/locks.rs
@@ -60,6 +60,12 @@ impl RawMutex {
 unsafe impl Send for RawMutex {}
 unsafe impl Sync for RawMutex {}
 
+impl Default for RawMutex {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 /// A guard representing an active lock on an [`RawMutex`].
 pub struct RawMutexGuard<'a>(&'a RawMutex);
 impl<'a> Drop for RawMutexGuard<'a> {
@@ -136,6 +142,7 @@ pub struct InitOnce<T> {
     is_initialized: Static<bool>,
     value: UnsafeCell<MaybeUninit<T>>,
 }
+
 impl<T> InitOnce<T> {
     /// Creates a new uninitialized object.
     #[must_use]
@@ -195,6 +202,13 @@ impl<T> InitOnce<T> {
         }
     }
 }
+
+impl<T> Default for InitOnce<T> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl<T> Drop for InitOnce<T> {
     fn drop(&mut self) {
         if self.is_initialized.read() {